The long-term objective of this proposed research is to understanding the mechanisms involved in the inheritance of DNA in prokaryotes. Maintenance of DNA molecules in growing populations of cells requires that the DNA be replicated and that the DNA molecules be distributed (partitioned) such that each daughter cell receives at least one copy of the replicon. The study of extrachromosomal replicons known as plasmids has been very important in our current understanding of these processes. Many plasmids-encode antibiotic resistance plasmids resistance genes and the role in the ability to treat patients in hospitals plays an important suffering from bacterial infection. A better understanding of the mechanisms involved in plasmid maintenance would potentially benefit an approach to their control in clinical settings. In addition, many important pharmaceutical products are made using plasmid-containing bacteria, and the stability of plasmids in such situations is important. Also, several viruses associated with human diseases are know to exist in a plasmid-like state in cells. Plasmid loci involved in plasmid maintenance in prokaryotes have been identified and characterized previously; however, knowledge of the interactions of plasmid components with cellular products is very limited. I propose to study partitioning of low copy number plasmids in E. coli, with the specific aim of identifying and characterizing plasmid interactions and how mechanistically they accomplish partitioning: Chromosomal mutants affected in partitioning of the low copy-number replicons F, Pl, pSClOl, or the chromosome will be isolated using a variety of genetic selections including effects on plasmid stability and extragenic suppression of plasmid oar mutations. The mutants will be analyzed using genetic and molecular techniques to determine what functions are affected and to begin to understand the roles they play in partitioning.